| Abstract: | Visible band imagery from the Nimbus 7 Coastal Zone Colour Scanner (CZCS) and other satellite scanners indicates the occurrence of well-defined and persistent patterns of fine sediment concentration in the Irish Sea. The principal features of these distributions are related to variations in the intensity of tidal stirring with sharp transitions in the sub-surface reflectance occurring at frontal boundaries where there are abrupt changes in the vertical mixing regime. Observations of the suspended sediment concentration, both direct and by optical beam transmittance meter, have been used to demonstrate the correspondence between seston variations and changes in sub-surface reflectance as observed by satellite scanners.Radiometric measurements of sub-surface reflectance R are used to investigate the dependence of R (550 nm) on the concentration of suspended particulates Σ. The slope of the Σ- R relation is found to increase with the concentration of organic seston in a systematic way, a trend which is also apparent in an independent data set from the mouth of the Rhoˆne in the Mediterranean.These results may provide the basis for improved quantitative determination of seston from remotely sensed data if the mean level of organic seston concentration is known, or can be estimated from the spectral ratios in the reflectance data. |
